1. Field of the Invention
The present invention relates to an improved functional polymer which can be used for an organic electroluminescence element or the like.
2. Description of Related Art
Electroluminescence elements employing an organic component have been studied as potential next generation flat display devices. In particular, when a low molecular compound is used to form a layered thin film by vacuum deposition, full-color display devices with high reliability can be produced. However, devices produced in such a manner are expensive and could not easily have a large area.
To cope with these disadvantages, organic electroluminescence elements (polymer type electroluminescence elements) have been proposed, which are composed of a thin film formed by application of a polymer including phenylenevinylene and fluorene as its basic skeleton, from a solution. Especially, polymers including fluorene as the basic skeleton have been found to achieve high emission efficiency. Although polyfluorene, obtained by polymerization of fluorene, emits blue light with an emission peak at a wavelength of approximately 430 nm in its fundamental unit, the emission properties are not stable and emission efficiency is relatively low. In view of this, a copolymer obtained by synthesizing fluorene with another structural unit has been proposed, as reported in Japanese Publication of Unexamined PCT Patent Application No. 11-510535 and Applied Physics Letters 74, 2265 (1999).
However, even when the copolymers disclosed in the above-referenced documents are employed, display of three primary colors (red, green, blue) as required full-color display can not be readily achieved.
Further, the molecular chains of fluorene are likely to align with each other because of the liquid crystal property of fluorene polymers. As a result, the molecular chains aggregate due to thermal motion such that excitation energy is transferred to the aggregation which then emits light. Typically, long wave light with a low energy level is emitted, which leads to an additional problem that blue emission cannot be obtained by conventional fluorene-based polymers.
The present invention was made in view of the foregoing problems of the related art, and aims to provide a functional polymer which is free from aggregation of high molecular chains and is capable of easily providing three primary colors.
To this end, according to the present invention, there is provided a functional polymer comprising a compound obtained by copolymerization of a fluorene unit and an acene unit having three or more benzene rings.
Further, in the above functional polymer, said acene unit is at least one of anthracene, naphthacene, or pentacene.
Further, the above functional polymer consists of copolymers of a fluorene unit and anthracence.
Still further, said acene unit has the right part of the following structure: 
wherein A through H are selected from alkyl, thioalkyl, alkoxy, aryl, aryloxy, thioaryl, heteroaryl, alkenyl, alkinyl, cyano, nitro, NHAr, NAr2, condensed heterocyclic compound and a substituent including fluorine; I and K through W are selected from C, O, N, P, S, and Si; R1 and R2 are selected from alkyl (iso or normal), cycloalkyl, acyl, heteroaryl and aryl, alkenyl, stylyl, alkinyl, cyano, nitro, NHAr, NAr2, and CF3; p and q are integer numbers which satisfy p+qxe2x89xa72; and n and m are integers equal to or greater than 1.
Further, in the above functional polymer, a ratio of said acene unit in the polymer skeleton is 15% or less.
Further, the above functional polymer is obtained by copolymerizing a monomer of the following formula and a fluorene monomer: 
wherein A through H are selected from alkyl, thioalkyl, alkoxy, aryl, aryloxy, thioaryl, heteroaryl, alkenyl, alkinyl, cyano, nitro, NHAr, NAr2, condensed heterocyclic compound and a substituent including fluorine; I and K through W are selected from C, O, N, P, S, and Si, R1 and R2 are selected from functional groups of alkyl (iso or normal), alkoxy, cycloalkyl, acyl, heteroaryl and aryl, alkenyl, stylyl, alkinyl, cyano, nitro, NHAr, NAr2, and CF3; and p and q are integer numbers which satisfy p+qxe2x89xa72.
According to each of the above-mentioned structures, a functional polymer having an emission function which is highly effective and highly stable, a reversible optical property, and a high carrier transport ability can be obtained.
Also, there is provided an organic electroluminescence element wherein the above functional polymer is used.
According to the above organic electroluminescence element, a planar light source which is highly effective and of low cost with large area as well as a full-color flat display can be implemented.
Further, there is provided an optical memory wherein the above functional polymer is optically excited to store information.
According to the above structure, a high-density optical memory can be implemented.
There is also provided a hole transport element wherein the above functional polymer is used.
Thus, an electrophotographic photoreceptor of high performance can be further implemented.